In blood cell typing and compatibility test procedures commonly used in clinics today, both agglutination tests and cell lysis tests are carried out in a liquid phase, that is, sera containing antibodies with or without complement to be tested are mixed with suspensions of the blood cells with respect to which blood typing or compatibility testing is to be evaluated. Normally, fixed volumes are employed.
Evaluation of agglutination test results requires the technician to distinguish agglutination of cells due to specific antigen-antibody molecular bridging from non-specific cell aggregation in which unrelated forces also cause some degree of clumping. The technician must also be able to distinguish free unagglutinated cells which may be present from clumped or agglutinated cells. This requires highly experienced personnel or precise particle sizing and counting with costly instruments. In addition, measurement of the degree of specific agglutination is either poorly semi-quantitative or is costly and complicated to perform.
While some instrumented tests for typing of red blood cells by agglutination have been developed, the equipment for these procedures is both costly and complicated to use. For example, one device which has been proposed for typing red blood cells by instrument is known as the "AutoAnalyzer" of Berkman et al. described in Transfusion, Vol. 11, No. 6, pp. 317 et seq. (1971), and of Rosenfield et al. described in Vox. Sang. 26:289-333, 1974. In the AutoAnalyzer, blood samples and antibody sera are combined under special circumstances in complex tubular coils designed to bring about agglutination. The sample from the reaction coils passes a "T" connection with the leg in a downward position so that agglutinates which are formed tend to be removed. Agglutination can be detected measuring the decrease in optical density of the effluent from the "T" carrying the non-agglutinated fraction (Berkman et al. and Rosenfield et al.), or by trapping very strong agglutinates from the "T" on filter paper (Shield et al., Transfusion, Vol. 9, p. 348, 1969).
An alternative device is known as the "Groupamatic" and can cost several hundred thousand dollars (see Garretta et al., Vox Sang., Vol. 27, p. 141, 1974). In the Groupamatic device, sera and blood cell suspensions are combined to produce agglutination. The presence of agglutination is detected by passing the suspension across two light beams, one of which passes through the center of the reaction cuvette while the other passes through the periphery. A difference in the transmission of the beams is taken as the measure of the strength of agglutination. Sophisticated circuitry is required, however, placing the instrument beyond the means of all but the largest blood bank operations.
All liquid-phase hemagglutination tests, be they manual, "AutoAnalyzer", or "Groupamatic", suffer from a series of problems. Firstly, the manual tests lack the sensitivity of the instrumented tests so that clinically-significant red cell antigen-antibody reactions may be indiscernible by even the most experienced personnel. Secondly, unnecessary and unwanted protein in the reaction mixture may actually interfere with the development of hemagglutination, and cannot be removed readily without significant loss or elution of antibody. Thirdly, the red cells of about 2% of persons are unsuitable for sensitive evaluation by AutoAnalyzer (and presumably also by Groupamatic). Fourthly, red cells lose their sensitivity to specific hemagglutination on storage at 4.degree. C., even for 2-3 weeks. Fifthly, not even the sensitive methods of Berkman et al. and Rosenfield et al. will detect all clinically-significant red cell antigen-antibody reactions. Lastly, "AutoAnalyzer" and "Groupamatic" tests are inefficient for the detection of minor cell population cohorts in samples containing mixtures of cells having different antigens. Even if a mixture is recognized, separation to allow separate measurement and assay of the cohorts is extremely tedious and can only be performed manually by the most experienced personnel.
Tests based upon immune lysis present no problems when the cell surface antigen-antibody reaction interacts efficiently with complement, as for tissue (e.g., HL-A) typing. Unfortunately, this is rarely true with human red cells where either the cell membrane antigen-antibody complex interacts inefficiently with complement or antibody concentration must be limited to prevent intense agglutination that will mechanically interfere with immune lysis.
These problems gravely affect the operation of blood banking serology laboratories where even routine red cell typing remains a time-consuming, manual operation that demands more skillful and experienced personnel than are available. Furthermore, relatively few blood banks can undertake lymphocytotoxic tests required for tissue typing. There are no direct immunologic tests available to determine the pre-transfusion compatibility of granulocytes, and only an indirect test for platelets, such as .sup.14 C-serotonin release. (While granulocytes and platelets may be assigned HL-A types by selected and appropriate tests, such typing will not guarantee their compatibility).